Titan's conditions could be just right to power US-sized colony

Saturn’s largest moon could suit human settlement – provided we can keep the lights on. Thankfully, Titan has several energy sources that might one day power a colony, an analysis shows.

For all its alien strangeness, Titan is remarkably Earth-like. A thick atmosphere protects its solid surface from damaging radiation and it is the only other place in the solar system with liquid on its surface. If humans were to one day live under the yellow haze of the moon’s skies, exploring its rolling dunes and ragged peaks or settling by the side of gently stirring hydrocarbon lakes, they would need energy to power their lives.

“I think long-term, after Mars, Titan’s probably the next most important place that people will have an extended presence,” says Ralph Lorenz, a planetary scientist at Johns Hopkins University in Maryland.

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To figure out how humans might be able to survive on the distant moon far in the future, Amanda Hendrix of the Planetary Science Institute and Yuk Yung at the California Institute of Technology analysed potential energy sources.

Mining the moon

Any robotic explorers sent to initially scout out Titan would rely on nuclear power, harnessing radioactive decay to generate electricity and stay warm. Humans might be able to do the same, packing supplies from Earth to make a nuclear power plant, then mining the moon to keep it fueled. However, without investigating Titan’s interior geology, the feasibility of this idea is mostly guesswork.

But the moon is rich in easily accessible methane, making it a potential refuelling point for rockets travelling even further from Earth. “As a resource for long-term, solar-system-wide civilisation, Titan would be a pivotal place,” Lorenz says.

Although it would be inefficient to combust hydrocarbons on the moon itself due to the lack of readily available oxygen, future inhabitants of Titan could add hydrogen to acetylene to generate power. However, despite the theoretical abundance of acetylene on the moon, scientists have yet to detect it on Titan’s surface.

“It’s possible we are missing it because it’s being masked by the atmosphere,” says Sarah Hörst, a planetary scientist at Johns Hopkins University.

Carving out rivers

Hydropower might also be problematic as Titan has little rain except rare downpours of intense flash floods every few decades. “It’s not exactly ideal for hydroelectric power generation,” says Hörst. “For a short period of time, rivers would have very, very fast flow, then they’d be dry again.”

Dams or waterwheels could generate power from hydrocarbons made liquid by Titan’s extremely low temperatures, but it could be difficult to get the liquid flowing as the largest lakes and seas are lower than surrounding terrain.

“The topography doesn’t make it impossible, it just makes it a very big engineering project to carve out a river that flows downhill out of the sea,” Hendrix says.

A better option could be to put turbines in the seas because Saturn creates strong tides on Titan. Its largest sea, Kraken Mare, experiences up to a metre of tidal change each day. Those tides all flow through a narrow constriction separating the northern and southern parts of the sea, Seldon Fretum, or as it is nicknamed, the Throat of the Kraken.

“The Throat of Kraken is basically the Strait of Gibraltar,” Lorenz says. “We’re pretty sure there’s a very strong flow of liquid back and forth every Titan day. If you want reliable power that you know is going to be accessible, that’s where I would go.”

Atmospheric winds

Wind power would be equally tempting yet challenging as a long-term power source. While sand dunes indicate that Titan must have had strong surface winds at some time in the recent past, we haven’t found any evidence that such winds still blow.

But the atmospheric circulation reverses direction twice a year, and strong winds have been revealed in the upper atmosphere by cloud tracking and the brief measurements the Huygens probe made in 2005 as it descended towards the moon.

“If we had wind machines in the upper atmosphere, we could generate power ten times greater than we do with wind turbines here on Earth,” says Hendrix. “We could have some sort of airborne wind turbines tethered to the surface.” Yet this type of wind turbine is beyond the capacities of current technology.

Harness the sun

The most unexpected idea is solar power. At almost 10 times the distance from the sun as Earth, Titan receives just one hundredth the sunlight. That light gets further filtered by atmospheric haze. “The brightest it ever is on Titan is like dusk on Earth,” Hörst says.

But solar panels are getting ever-more efficient and a human civilisation on Titan would have the space to construct extensive, permanent energy infrastructure.

“If you just build solar power plants that are large enough, they’ll generate plenty of energy,” says Hendrix. She and Yung estimate that supporting 300 million people – roughly the population of the United States – would require a solar farm covering 10 per cent of Titan, or the surface area of the entire US. By contrast, generating the same amount of power on Earth would take under 10 per cent of the surface of Kansas.

As on Earth, another challenge would be keeping the solar panels clean, in this case of organic molecules created in Titan’s atmosphere that would otherwise reduce their efficiency.

“On Titan, we’d also need to think about tholin sediments settling out of the atmosphere onto the panels and having to wipe them off every so often,” Hendrix says.

Titan has the energy resources to support a human civilisation, but living there would be tricky. Squeezed by 1.5 times Earth’s atmospheric pressure yet buoyant under one-seventh Earth’s gravity, humans on its surface would feel more like divers under an ocean than astronauts on exposed airless rocks in space.

Furthermore, Titan is cold with an unbreathable atmosphere of nitrogen, methane and hydrogen, so, like divers, anyone living there would need to wrap up and carry their air with them.

Whatever power source we might one day use on Titan, we will need to perfect it on Earth first.